This invention relates to methods for recovering platinum from an article or a component coated with a coating containing platinum aluminide.
Modern gas or combustion turbines must satisfy the highest demands with respect to reliability, weight, power, economy, and operating service life. In the development of such turbines, the material selection, the search for new suitable materials, as well as the search for new production methods, among other things, play an important role in meeting standards and satisfying the demand.
The platinum group metals (PGM) or PGMs (platinum, palladium, rhodium, iridium, osmium, and ruthenium) are becoming increasingly important to the global economy. The aviation industry uses precious metals in the manufacture of aircraft engines. Gold and silver, as well as palladium and platinum, are used in the manufacture of different types of aircraft engines. Typically, an aircraft engine has up to 23 parts that contain precious metals. Various aircraft engine parts that use precious metals include vanes, stators, blades, fuel nozzles, fuel manifolds, tobi ducts, and heat exchangers. Whereas parts of an aircraft's engine turbine system and avionics system use gold and silver, the aircraft blades use platinum. This invention relates to the recovery of platinum from used aviation components.
After the life of an aircraft engine is over, the aviation industry can still recover precious metal from aircraft engines and their parts. Until recently, platinum group metals (PGM) were recovered by classical precipitation procedures, which involved many repeated precipitation/re-dissolution stages in order to obtain metal of the desired purity. These processes are extremely tedious and time-consuming, with metal being tied-up in process often for many months.
Yet, recovery of precious metals can account for up to 50 percent of an aircraft engine's recycling value. With respect to platinum aluminide coatings, past methods involved removal of platinum aluminide by dissolving both the aluminum and platinum in strong acids, such as aqua regia. Platinum could then be recovered by treating the acidic solution containing dissolved platinum salts with a neutralizing base, thereby causing the dissolved platinum and aluminum salts to precipitate and be collected. This method has its drawbacks. A neutralization of the acidic solution is required to recover dissolved platinum from the acidic solution, thus adding contaminants to the recovered platinum. Additionally, the aluminum is also dissolved in the acidic solution, further contaminating the purity of the recovered platinum. Accordingly, there is a need for new and improved methods for recovering platinum from engine turbine blades.